More than 1,000 randomized computer simulations of how solar systems take shape are lending fresh support to an old question: was Earth's location in the solar system inevitable, or a fluke? According to new modeling described this week by planetary scientist Nader Haghighipour of the University of Hawaii at Manoa, the answer leans toward inevitable.
Haghighipour presented the work at the Origins 2026 conference in Paris, a joint meeting of the International Society for the Study of the Origin of Life and the International Astronomical Union's astrobiology commission. Rather than starting from the solar system's known layout, his models begin from randomized, non-uniform distributions of planetesimals and planetary embryos inside a young protoplanetary disk and let gravity and collisions run their course across more than 1,000 separate trial runs.
What the runs produced
An Earth-mass planet at roughly one astronomical unit from its star -- the Earth-sun distance -- emerged repeatedly across the simulations. A Venus-like body appeared in about 28 percent of runs, occasionally landing inside the star's habitable zone, and a smaller, Mars-like object consistently formed near its present-day orbital position. Advances in computing power have also cut the time needed to run each simulation from six to eight months down to six to eight weeks on a standard laptop, letting Haghighipour test far more starting conditions than earlier studies could manage.
The approach addresses a long-standing critique of solar system formation models: many earlier simulations quietly built in assumptions about where planets should end up, risking circular conclusions about how special, or ordinary, Earth's position really is. Haghighipour's models instead let outcomes emerge purely from disk physics.
There is no reason to believe that our Earth is a fluke.
Nader Haghighipour, planetary scientist, University of Hawaii at Manoa
He cautioned that the outcomes remain sensitive to starting conditions: small variations in initial conditions can have a great impact on the final product, meaning no two protoplanetary disks are likely to produce identical planetary systems even under similar physical rules.
The findings fit into a broader body of evidence from NASA's exoplanet surveys, which have identified thousands of rocky worlds orbiting sun-like stars, some within their habitable zones. If Earth-like planets in Earth-like orbits are a routine output of disk physics rather than a rare coincidence, that strengthens the case that habitable worlds could be common throughout the galaxy. Haghighipour's group is now working to fold in additional physics, including water delivery and moon-forming impacts, as the work moves toward formal publication.
